Miquel and Rodriguez—Terrestrial gastropods from Santa Cruz


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Figure 7. Patagocharopa enigmatica n. gen. n. sp.: (1–4) MPM PI 3336, holotype; (1) apertural view, arrows point the suture cicatrix; (2) detail of apertural teeth, arrows point the semi-internal barrier-teeth and lamellae; (3) apical view. Note: image (2) was digitally enhanced and modified to better visualize structures. Scale bars represent 500 µm(1, 3) and 200 µm(2).


be currently found in environments ranging from subtropical to cold, and from very humid to semiarid. The Vertiginids of the northern hemisphere inhabit a wide range of environments from costal dunes, swamp forests or woody talus slopes of northern Europe and North America, to open deciduous forests, treeless marshlands, and wet meadows of warm lowland areas of central regions of the Holarctic continents (Vavrovà et al. 2009). How- ever, some North American Vertiginidae are limited to xeric herbaceous-dominated prairies and shrublands (Nekola and Coles, 2001). In addition, South American records of Gastrocopta nodosaria occur in temperate and tropical regions of the country down to the northern area of Patagonia (Miquel and Aguirre, 2011). South American charopids are primarily mesic forest dwellers, but extend to dry and open scrublands of Andean-Patagonian forests in northwestern Patagonia (Miquel and Barker, 2009; Miquel and Bellosi, 2010). Punctidae species inhabit humus, and can be found on fallen leaves, under mesophytic bushes and trees (Pilsbry, 1948); particularly, in Juan Fernández Archipelago Punctum sp. dwells on the soil, among leaves and on ferns (Odhner, 1922). The species of Scolodonti- dae represent an important stock of the soil biota, mainly in


tropical rain forests, but they also can be found in dry forests, and a few in grasslands, being carnivorous (Ramírez, 1993). Thus, the families represented in the Santa Cruz Formation are not particularly informative about the paleoenvironmental conditions prevailing in the area during the Miocene, if the biology of the individual species is not considered. The fossil site is located, phytogeographically, in the


Patagonian Province (Cabrera, 1971), and zoogeographically it is located within the Patagonian Domain of the Andean- Patagonian Subregion (Ringuelet, 1961). Currently, the exten- sive xerophytic plateau of the Patagonian territory offers only few areas for the survival of land snails because of the dry and cold climate, with snowy winters, and strong winds and frosts during the whole year. This is reflected in the records of land snails from the region where collections mostly come from the mountain ranges and very few from the Patagonian plateau sensu stricto (Hylton Scott, 1963, 1968). The modern fauna is predominantly that of micromollusks of the family Charopidae with a much lower representation by species of Succineidae, Bulimulidae, Scolodontidae, Vertiginidae, and Macrocyclidae (Fernández, 1973).


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